Application on Round-base Coolers

If there's one thing our recent 33-Way Thermal Interface Material Comparison article has taught me, it's how the advice freely handed-out in discussion forums can often be wrong. After we wrote the article, many enthusiasts argued that spreading out the TIM with a latex glove (or finger cover) was not the best way to distrubute the interface material. Most answers from both the professional reviewer industry as well as enthusiast community claim that you should use a single drop "about the size of a pea". Well, we tried that advice, and it turns out that maybe the community isn't as keen as they thought. The image below is of a few frozen peas beside a small BB size drop of OCZ Freeze TIM. The image beside it is of the same cooler two hours later after we completed testing.

Decidedly, the BB size seems to be a much more appropriate amount for the PGA-478 application since it easily covered the one-inch round copper core of this Intel cooler and then some. Our images above have done sufficiently for depicting how much TIM should be used in a socket 478 cooler, but that's old news.

To begin our experiments, we have started with the most basic of all designs. Circular coolers are very common equipment, with the product list spanning from small Intel-supplied stock cooler up to the larger Thermaltake MaxOrb aftermarket cooler. But while the round outer design may be popular to designers, it is much less common to find a circular base as the contact surface. To the best of my knowledge, the only coolers I have ever seen with this finish are those from Intel, but I digress. The design has its pros and cons, and regardless of cooling performance the round base is among the easiest to properly apply thermal paste to.

Because the raised copper center core is circular, the most logical application pattern is going to match the shape. A single drop of thermal paste roughly half the size of a BB is placed at the center of the cooler, which will theoretically spread evenly in every direction as pressure is applied.

In all of our experiments, the images showing the depressed material once it has been spread out were all taken only moments after mounting the cooler. The thermal material is not allowed to cure, and the system is not powered on to begin thermal cycles. This is all done so that you can see the initial impact of mounting pressure and the direction that Thermal Interface Material travels. Please note that allowing the system to complete a few initial thermal cycles will thin the viscosity of the material and level out the paste, which will also allow it to bleed out towards the edges.

Judging from our cold test, a single round drop of thermal paste roughly half the size of a BB is more than sufficient to cover the entire mating surface of a stock Intel-included cooler. Ideally, you will want to use slightly less material than the amount shown above. Just remember that once heat is applied to thermal grease the viscosity will thin and spread out towards the edges just a little more, allowing the surfaces to come into closer (or direct) contact with each other. Keep in mind that thermal paste is only meant to fill the gaps, not coat the surface; perfectly flat metal on metal with no material in-between is your ultimate goal.

Benchmark Reviews invites you to share your comments and suggestions for this topic in our Discussion Forum.

Comments

Thanks Benchmarkreviews for this is a very informative article.This kind of quality reviews makes it a lot easier for enthusiasts, like me, which do not have much resources for us to try such tests.Thanks again... and i hope for more quality reviews from you guys..

Thank you for researching and publishing your work on applying thermal paste. I don't have a HDT heat sink, but the design is exactly the same as the Cooler Master Hyper 212 Plus Direct (blah blah the name is sooooo long).

Thank you for a well written and presented article. I recently purchased a Xigmatek 'Red Scorpion' cooler to replace my stock Intel LGA775 cooler. Now I know how to best apply the paste! Also, my Red Scorpion was supplied with the white thermal paste, thanks again for explaining what these compounds are made from. I will throw out the white paste and get some that has a high silver content.Cheers!

Olin, under the section "Heatpipe Directional Orientation" are you stating that it is better for the CPU cooling fan to point toward the top of the case, rather than front to back? I would think this would be true for PC cases that have the PSU mounted on the bottom of the case, and have a fan at the top, blowing outward. The new Lian Li PC-A04 case is a perfect example of this. Can you comment? (Thanks!) Perhaps a picture would be helpful here.

In further reading, I realize that I didn't catch what you were explaning. I do understand what you are saying now. But my additional point/question is still relevant. If you take a look at the Lian Li PC-A04 case, wouldn't it make sense to re-orient the CPU cooler towards the top of the case? (They actually do not include a rear fan.) I would think that a vertical orientation of the heat pipes, along with a bottom to top fan direction would be optimal, considering that hot air rises.

As you've stated, heat rises. Additionally, despite capillary action gravity still affects the heat-pipe fluid. It's best to orientate the heatsink so that heat-pipes are either level or collecting fluid at the base.

Assuming that "BB" size is equal to 4,57 mm and "BBB" to 4,83, and as "LGA775" is 37,5 x 37,5 millimetres, and on the picture with the peas the pea is approximately 1/3rd of the diameter which results in 12,5 mm. which is 1,25 cm I do arrive to the conclusion that in you country agronomy is really advanced. In my country peas are generally around half a centimetre, which make them BBB size and almost BB size. So, in conclusion, the communityis still as keen as it thought, or in other words, it is not mistaken - your peas are mistaken ( they are really f***** up ;) ). I do hope this is cleared out, and I do hope that somebody confirms the size of the peas on the picture, based on my assumptions!

These were frozen peas, and they are slightly larger than a pencil eraser. In the photo, that bit of thermal paste was roughly half the mass of a BB, and it covered the entire contact base on an old LGA775 cooler.

The peas being referred to by the term "the size of a pea" (and in the fable "The Princess and the Pea") are the peas you make pea soup out of, which are dried peas. Dried peas are much smaller than frozen peas, about the size of the TIM you used in the now infamous frozen peas picture. But instead of peas, I had heard the amount to place was the size of a rice grain which also works and is less confusing.

On a different subject, I would liked to have seen the results of mounting the square cooler that you did a thin, even spread of TIM on. How did it look when removed?

Also I would like to see heat readings from all these different application methods. While you may want one or the other spreads visually, how does that translate into actual practice? Could less coverage translate into a thinner layer that increases metal to metal contact, yielding better results than 100% CPU coverage but thicker layer? Inquiring minds want to know!!

^Where you have pipes on the heatsink base, there are tiny dips as the surfaces meet, the base is not 100% flat, therefore it is vital that you ensure these channels are filled with paste to properly conduct the heat away from the processorMoto

Hi Olin. I found your article to be extremely informative, thanks. I was wondering if you could shed some further light on whether or not failure to sand down an HDT cooler would make any significant difference for a pc that is never going to be overclocked at all. I would particularly appreciate your views on the Coolermaster Hyper TX3 cooler, which looks as if the the pipes are set too deep into the mounting base. See links below.

After having read your article, I have concluded that the two drops on the two centre partitions of the mounting base would be the best option for the Hyper TX3 cooler (to be used with an AMD Phenom II x6 1100T CPU), however, if sanding is not carried out, how would one deal with the space between the deeply set pipes and the CPU surface? Also, I have read that even merely touching the metal with a finger can cause grease and all kinds of particles to become stuck to it, so if sanding were to be carried out, how could one possible ensure that the cooler is thoroughly cleaned of all the residue from sanding? Thank you for any advice.